Current consumption control device

Abstract

A device for controlling the current consumption of a power supply which applies a voltage to a transmission control circuit for transmitting a transmission signal with respect to a transmission line is provided. A power supply stabilizing circuit for stabilizing a voltage applied from the power supply; an amplitude detection circuit for detecting a transmission signal input from the transmission line; a switching circuit for interrupting application of a voltage from the power supply stabilizing circuit to the transmission control circuit; and a control circuit for controlling the open/closed state of the switching circuit according to the presence or absence of a transmission signal detected by the amplitude detection circuit are provided, and only when the amplitude detection circuit has detected the transmission signal, the control circuit sets the switching circuit into the closed state so as to permit a voltage to be applied to the transmission control circuit. When no transmission signal is transmitted, application of an unnecessary voltage to the transmission control circuit is interrupted, thereby reducing the current consumption.

What is claimed is: 
     
       1. A device for controlling the current consumption of a power supply, comprising: power supply stabilizing means for stabilizing a voltage generated by said power supply and for producing a stabilized voltage;   transmission control means for transmitting a data transmission signal on a transmission line, said transmission control means being selectively powered by the stabilized voltage;   interface means for connecting said transmission control means and said transmission line, said interface means being selectively powered by the stabilized voltage;   detection means for detecting the data transmission signal on said transmission line and for outputting a detection signal when the data transmission signal is detected, said detection means being supplied with and powered by the stabilized voltage;   openable and closeable interrupting means for supplying the stabilized voltage from the power supply stabilizing means to said transmission control means and to said interface means when said interrupting means is in closed state, and for interrupting supply of the stabilized voltage from the power supply stabilizing means to said transmission control means and to said interface means when said interrupting means is in an open state; and   a central processing unit for controlling the opening and closing of said interrupting means in accordance with the detection signal output by said detection means.   
     
     
       2. The device according to claim 1, wherein said central processing unit is supplied with and powered by the stabilized voltage produced by said power supply stabilizing means. 
     
     
       3. The device according to claim 1, wherein said detection means and said central processing unit are continuously supplied with and powered by the stabilized voltage produced by said power supply stabilizing means. 
     
     
       4. The device according to claim 1, wherein said central processing unit controls said interrupting means to be set in the open state when said detection means detects that no transmission signal is being transmitted, and wherein said central processing unit controls said interrupting means to be set in the closed state when said detection means detects that the transmission signal is being transmitted. 
     
     
       5. The device according to claim 1, wherein said central processing unit includes means for receiving the detection signal output by said detection means, and controls said interrupting means to be set in the closed state when the detection signal is received. 
     
     
       6. The device according to claim 1, wherein said interrupting means includes a switching circuit means for selectively making or breaking a connection between said power supply stabilizing means and said transmission control means, and for selectively making or breaking a connection between said power supply stabilizing means and said interface means. 
     
     
       7. The device according to claim 1, further comprising a timer circuit means for keeping said interrupting means in the closed state for a preset period of time. 
     
     
       8. The device according to claim 7, wherein said timer circuit means keeps said interrupting means in the closed state until said central processing unit controls said interrupting means to be set in the open state. 
     
     
       9. The device according to claim 1, wherein said central processing unit further receives the transmission signal and carries out a predetermined function control on the basis of the transmission signal, said central processing unit being supplied with and powered by the stabilized voltage.